Merge pull request #61740 from abbradar/nested-chrootenv

Support nested user chrootenv environments
This commit is contained in:
Nikolay Amiantov 2019-05-30 15:53:12 +03:00 committed by GitHub
commit 6723d59ae9
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@ -7,32 +7,43 @@
#include <sched.h>
#include <unistd.h>
#include <sys/mount.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <sys/wait.h>
#include <sys/syscall.h>
#define fail(s, err) g_error("%s: %s: %s", __func__, s, g_strerror(err))
#define fail_if(expr) \
if (expr) \
fail(#expr, errno);
#include <ftw.h>
const gchar *bind_blacklist[] = {"bin", "etc", "host", "real-host", "usr", "lib", "lib64", "lib32", "sbin", NULL};
#include <sys/mount.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <sys/wait.h>
int min(int a, int b) {
return a > b ? b : a;
int pivot_root(const char *new_root, const char *put_old) {
return syscall(SYS_pivot_root, new_root, put_old);
}
const gchar *bind_blacklist[] = {"bin", "etc", "host", "usr", "lib", "lib64", "lib32", "sbin", NULL};
void mount_tmpfs(const gchar *target) {
fail_if(mount("none", target, "tmpfs", 0, NULL));
}
void bind_mount(const gchar *source, const gchar *target) {
fail_if(g_mkdir(target, 0755));
fail_if(mount(source, target, "bind", MS_BIND | MS_REC, NULL));
fail_if(mount(source, target, NULL, MS_BIND | MS_REC, NULL));
}
void bind_mount_host(const gchar *host, const gchar *guest) {
const gchar *create_tmpdir() {
gchar *prefix =
g_build_filename(g_get_tmp_dir(), "chrootenvXXXXXX", NULL);
fail_if(!g_mkdtemp_full(prefix, 0755));
return prefix;
}
void pivot_host(const gchar *guest) {
g_autofree gchar *point = g_build_filename(guest, "host", NULL);
bind_mount(host, point);
fail_if(g_mkdir(point, 0755));
fail_if(pivot_root(guest, point));
}
void bind_mount_item(const gchar *host, const gchar *guest, const gchar *name) {
@ -44,19 +55,22 @@ void bind_mount_item(const gchar *host, const gchar *guest, const gchar *name) {
}
void bind(const gchar *host, const gchar *guest) {
mount_tmpfs(guest);
pivot_host(guest);
g_autofree gchar *host_dir = g_build_filename("/host", host, NULL);
g_autoptr(GError) err = NULL;
g_autoptr(GDir) dir = g_dir_open(host, 0, &err);
g_autoptr(GDir) dir = g_dir_open(host_dir, 0, &err);
if (err != NULL)
fail("g_dir_open", errno);
const gchar *item;
while (item = g_dir_read_name(dir))
while ((item = g_dir_read_name(dir)))
if (!g_strv_contains(bind_blacklist, item))
bind_mount_item(host, guest, item);
bind_mount_host(host, guest);
bind_mount_item(host_dir, "/", item);
}
void spit(const char *path, char *fmt, ...) {
@ -72,11 +86,6 @@ void spit(const char *path, char *fmt, ...) {
fclose(f);
}
int nftw_remove(const char *path, const struct stat *sb, int type,
struct FTW *ftw) {
return remove(path);
}
int main(gint argc, gchar **argv) {
const gchar *self = *argv++;
@ -85,15 +94,7 @@ int main(gint argc, gchar **argv) {
return 1;
}
if (g_getenv("NIX_CHROOTENV"))
g_warning("chrootenv doesn't stack!");
else
g_setenv("NIX_CHROOTENV", "", TRUE);
g_autofree gchar *prefix =
g_build_filename(g_get_tmp_dir(), "chrootenvXXXXXX", NULL);
fail_if(!g_mkdtemp_full(prefix, 0755));
g_autofree const gchar *prefix = create_tmpdir();
pid_t cpid = fork();
@ -119,9 +120,24 @@ int main(gint argc, gchar **argv) {
spit("/proc/self/uid_map", "%d %d 1", uid, uid);
spit("/proc/self/gid_map", "%d %d 1", gid, gid);
bind("/", prefix);
// If there is a /host directory, assume this is nested chrootenv and use it as host instead.
gboolean nested_host = g_file_test("/host", G_FILE_TEST_EXISTS | G_FILE_TEST_IS_DIR);
g_autofree const gchar *host = nested_host ? "/host" : "/";
bind(host, prefix);
// Replace /host by an actual (inner) /host.
if (nested_host) {
fail_if(g_mkdir("/real-host", 0755));
fail_if(mount("/host/host", "/real-host", NULL, MS_BIND | MS_REC, NULL));
// For some reason umount("/host") returns EBUSY even immediately after
// pivot_root. We detach it at least to keep `/proc/mounts` from blowing
// up in nested cases.
fail_if(umount2("/host", MNT_DETACH));
fail_if(mount("/real-host", "/host", NULL, MS_MOVE, NULL));
fail_if(rmdir("/real-host"));
}
fail_if(chroot(prefix));
fail_if(chdir("/"));
fail_if(execvp(*argv, argv));
}
@ -130,10 +146,7 @@ int main(gint argc, gchar **argv) {
int status;
fail_if(waitpid(cpid, &status, 0) != cpid);
// glibc 2.27 (and possibly other versions) can't handle
// an nopenfd value larger than 2^19
fail_if(nftw(prefix, nftw_remove, min(getdtablesize(), 1<<19),
FTW_DEPTH | FTW_MOUNT | FTW_PHYS));
fail_if(rmdir(prefix));
if (WIFEXITED(status))
return WEXITSTATUS(status);